This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Swedish Patent Application No. 0101984-3 filed on May 31, 2001, the entire content of which is incorporated herein by reference.
The present invention relates to a device, computer program product and method for indicating a function deviation of one or more details of manufacturing equipment using frequency component analysis for analyzing deviations from a nominal product shape and an actual product shape using surface data of a physical surface describing the present product shape, the product having been processed by the manufacturing equipment. It also relates to a device for indicating the quality of a product processed by the manufacturing equipment.
The invention also relates to a method of configuring a frequency map comprising a set of function deviation indicating frequencies, the map being intended to be used in a device for indicating a function deviation of one or more details of a manufacturing equipment.
One way of obtaining indications of whether there are problems in manufacturing equipment is to use a vibration sensor to sense vibrations of the manufacturing equipment. A frequently used method of analyzing the vibrations is based on the Fourier analysis.
In U.S. Pat. No. 4,453,407 to Sato et al., assigned on its face to Hitachi, a vibration diagnosis method and apparatus for rotary machines are presented. It is adapted for measuring the vibration of a rotor shaft of a rotary machine, extracting the vibration component synchronous with the revolution of the rotor shaft from the measured vibration data, comparing the amplitude of the extracted vibration component with the amplitude of the overall vibration, analyzing the causes of the synchronous vibration component when the result of the comparison meets a predetermined reference, judging, in accordance with the result of the analysis, whether the vibration due to mass unbalance is attributable to an abrupt generation of mass unbalance or to a thermal bow of the rotor shaft, and displaying the result of the judgment.
In U.S. Pat. No. 4,425,798 to Nagai et al., assigned on its face to Kawasaki Steel, an apparatus for diagnosing abnormalities in rotating machines is presented. It is intended to be used for the diagnosis of rotary machinery equipment and utilizes a fast Fourier transform frequency spectrum analysis system. The presence or absence of an abnormality or trouble in the rotating machinery is determined by selecting high amplitudes out from the frequency spectrum computed by the FFT frequency spectrum analysis system, arithmetically processing distribution data of spectrum amplitudes adjacent each frequency giving the corresponding high amplitude, and detecting the amplitude, at which the frequency of vibrations of the rotating machinery has attained a maximum value, together with such a frequency.
In the fields of diagnosing and monitoring machinery equipment, Fourier analysis has been used as disclosed in DE 40 17 448 A1 and DE 40 32 299 A1.
Approaches of the kinds presented above are intended to be used to diagnose machinery equipment so that they do not malfunction and start to machine products of too low quality. A common feature of the inventions disclosed in the documents above is that the diagnosis is based on vibrations detected by sensors.
It has been realized that there are a lot of vibrations in machinery equipment to be detected by these sensors and that not all of the vibrations that can be detected in a machinery equipment lead to products of too low quality. This means that there are vibrations in machinery equipment that do not jeopardize the quality of the product. Since not all vibrations impede the quality of the product there is a risk that the presence of harmless vibrations makes it difficult to detect harmful vibrations.
Thus, it has been realized that measuring vibrations using vibration sensors on machinery equipment can lead to the disadvantage of having to deal with vibrations that do not effect the quality of the product being machined.
According to one aspect of the present invention, there is provided a device for indicating a function deviation of one or more details of manufacturing equipment using frequency component analysis. An example of a detail is a pulley, which is arranged in manufacturing equipment. Other examples of details will be presented below. The frequency component analysis can be used to analyze deviations between a nominal product shape and an actual product shape of a product using surface data of a physical surface describing the actual product shape, the product having been processed by the manufacturing equipment. The nominal product shape is the shape of a product if it had been manufactured in a perfect machine with no limitations when it comes to precision. It can also be seen as the xe2x80x98theoreticalxe2x80x99 shape. The actual product shape (or present product shape) is the shape the product actually has. This shape is likely to vary between products intended to have the same nominal shape. It can be seen as the xe2x80x98practicalxe2x80x99 shape.
The analysis can be based on the surface data and a set of function deviation indicating frequencies corresponding to frequencies at which function deviations occur in the one or more details. The function deviation frequencies can be comprised in a frequency map.
The device comprises an input connection, a memory comprising the frequency map, an indicator, and a computational means for receiving the surface data via the input connection, performing a Fourier transformation of the surface data, and indicating, using the indicator, the correspondence between the frequency components of the surface data and the function deviation indicating frequencies of the frequency map. These steps are responsive for performing the actual indication of a function deviation.
Analyzing how the actual product shape of a product having been processed by the manufacturing equipment varies in relation to the nominal product shape can be used as an indication of the state of the manufacturing equipment.
Surface data of a physical surface of the actual product shape describes the present (actual) product shape as it as been processed by the manufacturing equipment.
The surface data can originate from an actual surface of a rotational surface or a plane surface, for example.
Analyzing the product processed by the manufacturing equipment is advantageous since only the frequencies that affect the actual product shape is detected. This means that vibrations not resulting in a change of the actual product shape do not impede the indication. Also, it is not necessary to test every product to see whether there are problems in the manufacturing equipment. It is sufficient to test only a fraction of the products processed by a the equipment. This means that the present invention does not have to be used on a continuous basis. Another advantage is that a product can be analyzed after it has been manufactured. With other solutions this is not possible since the vibration data is normally not present at later times. This is because the Fourier analyses of other approaches are based on time directly, but in the present invention the Fourier analysis is based on a mark or a deviation of the actual product shape. Thus there is a spatial aspect of the Fourier analysis as suggested in the present invention.
Exemplary details of manufacturing equipment are details operating with frequencies, including overtones for rotating equipment within the manufacturing equipment, such as a rotary shaft, drive motor and belts. For instance, if a belt has become worn, the present invention will indicate that a function deviation has occurred, provided that there is an effect on the products manufactured by the manufacturing equipment. One feature of relevance here is relationships of revolutions of one detail and effects of these revolutions on other details within the manufacturing equipment.
The analysis can be based on the surface data of the actual product shape and a set of function deviation indicating frequencies corresponding to frequencies at which function deviations occur in the one or more details of the manufacturing equipment. This leads to an advantage of being able to indicate a probable cause of the deviation in the actual product shape. The function deviation indicating frequencies can be comprised in a frequency map.
In one embodiment the computational means can be further configured for comparing frequency components of the surface data with the function deviation indicating frequencies of the frequency map and for indicating, using the indicator, in case a correspondence is detected between at least one frequency of the set of function deviation indicating frequencies of the frequency map and at least one frequency component of the surface data. After indication, the function deviation can be further examined and later alleviated so that the manufacturing equipment can go back to its normal working conditions.
In another embodiment the correspondence can be arranged to be based on the correlation between the frequency components of the surface data and the function deviation indicating frequencies of the frequency map. Thus, for example, a correlation exceeding a predetermined level leads to an indication that the presence of a function deviation has occurred. By analyzing what frequency component is responsible for the indication the function deviation can be found and alleviated.
According to another embodiment the surface data can correspond to a line along the surface of the product. In one example, the line can have an orientation in a processing direction of the manufacturing equipment. In another example, the line can have an orientation in which at least a component of the line is in the processing direction of the manufacturing equipment.
Situations in which a line is in the processing direction can be found, for instance, in paper mills and rolling mills, in which paper and steel are manufactured in the processing direction. In some cases the line is not limited to being in the processing direction of the product. However, the line should comprise a vector component that covers the variation of the surface to be measured and analyzed. Also that vector component must be able to be isolated. For instance, a line being sampled diagonally in relation to a processing direction over a nominal flat surface can be seen as comprising two vector components: one in the processing direction and one in a perpendicular direction. Depending on what vector is of interest, a proper one can be chosen and subjected to Fourier transformation.
In one embodiment the surface data can be in the form of two-dimensional surface data of the physical surface to be analyzed. In this case the computational means can be further configured for forming one dimensional surface data from the two dimensional surface data, i.e. to select data forming a line along the surface. This offers the advantage that from a sample of a physical surface it is possible to form more than one line which results in increased opportunities of performing more than one frequency analysis using the present invention.
In another embodiment the surface data can be one dimensional and can be transferred using a one dimensional Fourier transform. In another embodiment the surface data can be two dimensional and can be transformed using a two dimensional Fourier transform.
In another embodiment the device can be configured to be portable or stationary. A portable device is advantageous when performing on site analysis, and a stationary device is advantageous when used in a competence center.
In another embodiment the Fourier transformation can be one of the fast type and the continuous type. Today, in the digital world, the fast Fourier analysis is advantageous but it should be pointed out that the continuous Fourier transform can be employed to fully reach the potentials of the present invention. It should also be noted that the present invention can be carried out by combining analogue and digital electronics. For instance, a specially designed electronic circuit may be employed to send an output signal to a computer screen for indicating presence of a function deviation.
In another embodiment the computational means can be a digital computer.
In another embodiment the frequency map can be comprised in a memory located at one location, the computational means can be located at another location, and the memory and the computational means can be interconnected by a computer network. This opportunity offers the advantage of having frequency maps at different levels 1) a manufacturing unit; 2) a set of manufacturing units of a plant; 3) a set of manufacturing units of a company.
A computer network offers an opportunity of analyzing manufacturing units at a location distant from the memory. This is advantageous when assessing the condition of manufacturing equipment.
In another embodiment the input connection can be coupled to a communication network. This facilitates the opportunity of obtaining surface data electronically. This is advantageous since time is saved using this option. Also, this is advantageous since this means that the analysis does not have to be performed on site. It can also be performed on an aggregate level.
In another embodiment the input connection can be coupled to a disk drive station of a computer. This facilitates the opportunity of obtaining surface data on a disk. This is advantageous since this means that the analysis does not have to be performed on site.
An alternative use of the present invention is to use it to indicate the quality of the product. However this does not require the use of the frequency map but only the frequency components that indicate the physical surface of the actual product shape. This offers the advantage of obtaining information concerning the quality of the product.
The present invention can be used with different kinds of manufacturing equipment, for instance in manufacturing equipment for grinding, hot rolling, cold rolling, turning, milling, printing, polishing, and honing.
According to one embodiment the indicator can comprise a computer screen. Thus, when the device detects a function deviation in a product machined by the manufacturing equipment, the device can indicate this using the computer screen.
According to another embodiment the indicator can comprise an alarm. Thus, when the device detects a function deviation in a product machined by the manufacturing equipment, the device can indicate this by sending an alarm.
According to another aspect of the present invention, there is provided a method for indicating a function deviation of one or more details of manufacturing equipment. The method can be carried out, for example, using a device comprising an input connection, a memory comprising a frequency map, an indicator, and a computational means. The method can use frequency component analysis for analyzing deviations between a nominal product shape and an actual product shape of a product using surface data of a physical surface describing the actual product shape, the product having been processed by the manufacturing equipment. The analysis can be based on the surface data and a set of function deviation indicating frequencies corresponding to frequencies at which function deviations occur in the one or more details, the function deviation indicating frequencies being comprised in a frequency map. The method comprises receiving the surface data, e.g., via the input connection, performing a Fourier transformation of the surface data, and indicating, e.g., using the indicator, the correspondence between the frequency components of the surface data and the frequency map.
In addition, the method can further comprise comparing the frequency components of the surface data with the frequency map, and indicating in case a correspondence is detected between at least one frequency of the set of function deviation indicating frequencies of the frequency map and at least one frequency component of the surface data.
The method can be performed either on site or at a distant location, for instance, at a so called competence center.
According to another aspect of the present invention, there is provided a computer program product, which is loadable into the internal memory of a computer, comprising software code portions for performing the steps of the above-noted method, when run on a computer. This aspect facilitates the opportunity of using a general purpose computer, a PC, to perform the analysis. Distributing computer software today, can for instance be done by distributing a carrier, such as a CD-ROM, which is one embodiment of this aspect of the present invention. Computer software can also be distributed from an Internet web-site from which it is possible to download the computer program product. Thus, a computer program product can comprise, for example, a carrier, such as a CD-ROM, or a downloadable set of computer instructions that can cause a computer to perform the steps of the above noted method.
According to another aspect of the present invention, there is provided a method for indicating a function deviation of one or more details of manufacturing equipment using frequency component analysis for analyzing deviations between a nominal product shape and an actual product shape of a product using surface data of a physical surface describing the actual product shape, the product having been processed by the manufacturing equipment. The analysis can be based on the surface data and a set of function deviation indicating frequencies corresponding to frequencies at which function deviations occur in the one or more details. The function deviation indicating frequencies can be comprised in a frequency map. The method comprises receiving the surface data, performing a Fourier transformation of the surface data, comparing frequency components of the surface data with the frequency map, and indicating a correspondence between the frequency components of the surface data and the frequency map. An advantage of this aspect is that, in cases where the test frequency of products manufactured by the manufacturing equipment is low, the need of having an electronic device indicating manufacturing equipment status using a product manufactured by the manufacturing equipment is lower, perhaps even obsolete, since the actual indicating can be achieved using a lower level of electronic presence.
According to another aspect of the present invention a method of configuring a frequency map of a memory is disclosed. The frequency map comprises a set of function deviation indicating frequencies. The map is intended to be used in a device for indicating a function deviation of one or more details of a manufacturing equipment. The method comprises investigating function deviation indicating frequencies occurring in the manufacturing equipment, and inputting relevant function deviation indicating frequencies into the memory.
The investigation step can comprise scanning the manufacturing equipment for details that can produce function deviation indicating frequencies, and setting numerical values to the function deviation indicating frequencies of the details. These latter steps can be performed, for example, by an individual.
The information that is necessary to perform these steps can be found, for instance, in product manuals and maintenance manuals. Alternatively, this information can be obtained by an on-site investigation of the manufacturing equipment.